For the slow cooker: Spray your slow cooker with nonstick cooking spray - I used my EVO. Add sliced onions and garlic to the bowl and then cover with chicken breasts. Add chopped tomatoes, balsamic vinegar, olive oil, crushed red pepper (if using), salt and pepper. Cover and cook on low for 7-8 hours or high for 3-4 hours. Add basil and top with grated mozzarella cheese. Turn slow cooker on high and cover until the cheese has melted. Serve with brown rice, quinoa, whole grain or gf pasta, or zoodles! Yum! For the Instant Pot: Spray your Pressure Cooker with cooking oil spray and hit the saute function. Saute your onions until they begin to caramelize. Turn off saute and add in garlic and chicken, then top chopped tomatoes, balsamic vinegar, olive oil, crushed red pepper (if using), salt and pepper. Cover and set to manual for 15 minutes. After cook time, carefully switch to quick release and open the top of your pressure cooker when all the steam has released. Switch to saute and add in the mozzarella cheese and basil. Cook on saute until the cheese melts (2-3 minutes). Serve with brown rice, quinoa, whole grain or gf pasta, or zoodles! Yum!